http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
정사각형 콘크리트 구조물의 파쇄도 향상을 위한 비폭성 파쇄제와 천공 홀의 효과적인 배치
조황기,남윤민,김경진,이재하,손동우 한국전산구조공학회 2017 한국전산구조공학회논문집 Vol.30 No.2
As an alternative to conventional explosive methods for demolition of concrete structures and rocks, the use of non-explosive demolition agents can be considered to reduce noise, vibration, and dust emissions during the demolition process. In this study, we conduct finite element analysis for crack initiation and propagation caused by the expansion of non-explosive demolition agents in square concrete structures. The predicted crack patterns are compared with the experimental results in the literature. The minimum values of the required expansion pressure of non-explosive demolition agents are also estimated, which depend upon the arrangement of non-explosive demolition agents and empty holes. Furthermore, we investigate the effect of empty holes on the fragmentation of concrete structures, and discuss the effective arrangement of non-explosive demolition agents and empty holes for fragmentation improvement.
로터 굽힘의 국부적 교정을 위한 전자기 유도가열 공정의 다중물리해석
조황기(Hwangki Cho),박민규(Min-Gyu Park),박현구(Hyun-Ku Park),박광하(Kwang-Ha Park),손동우(Dongwoo Sohn) 대한기계학회 2017 대한기계학회 춘추학술대회 Vol.2017 No.11
A bending deformation of steam turbine rotors can lead to serious accidences in the power plant. Therefore, the bent rotors should be straightened in an appropriate manner. Among several straightening methods, an electromagnetic induction heating is considered a promising tool in terms of efficiency and accuracy. In this study, we develop a finite element procedure for multi-physics simulation that includes electromagnetic induction, heat transfer, as well as thermo-elasto-plastic deformation. The difference in coupling strategies of multi-physics phenomena is also discussed. Subsequently, we conduct a series of numerical simulations for local straightening of bent rotors considering the states of initial residual stresses.
정사각형 콘크리트 구조물 분리를 위한 비폭성 파쇄제와 구멍의 효과적인 배치
조황기(Hwangki Cho),남윤민(Yunmin Nam),손동우(Dongwoo Sohn) 대한기계학회 2016 대한기계학회 춘추학술대회 Vol.2016 No.12
As an alternative to conventional explosives for breaking rocks and concrete structures, the non-explosive demolition agents are used to reduce noise and vibration in the demolition process. This study is concerned with numerical simulations of quasi-static crack propagation, in which the thermal expansion of circular non-explosive demolition agents causes the formation of crack in a square concrete structure. The concrete damage plasticity model is used to predict the crack patterns. In addition, we consider empty holes that can affect the crack patterns. Consequently, we discuss the effective arrangement of non-explosive demolition agents and empty holes to increase the number of broken pieces.
무근콘크리트 해체시 무소음화학팽창제의 최소요구팽창압 예측
김경진,조황기,손동우,구재현,이재하 한국전산구조공학회 2018 한국전산구조공학회논문집 Vol.31 No.5
도심지나 문화재가 인접한 지역 등의 소음, 진동 등 기존 발파해체 공법이 제한적인 조건에서 사용할 수 있는 구조물 해체 공법으로 무소음화학팽창제(soundless chemical demolition agent, SCDA)를 이용한 공법이 있다. 그러나 SCDA의 사용에 대한 기준이나 가이드라인에 참고될 만한 연구는 미미한 실정이다. 이 연구에서는 실내실험을 수행하여 강관의 길이, 외부수분차단, 수화열 발산 등의 다양한 조건에 따른 SCDA의 팽창압 발현 특성을 확인하였다. 또한 SCDA의 최소요구팽창압 예측을 위한 해석모델(자유단 1면, 고정단 3면의 직사각형 모델)을 개발하고 주요변수해석(홀 간 거리, 콘크리트 압축강도)을 수행하였다. 이 연구의 해석결과를 활용하여 자유단으로부터 콘크리트 구조물의 박락을 효과적으로 유도할 수 있을 것으로 판단된다. In construction site, conventional methods such as jackhammer or explosive methods(dynamite) have been often used for the demolition of structures. Use of those methods are more carefully treated in environmentally and historically sensitive area. For those reasons, use of Soundless Chemical Demolition Agent(SCDA) is getting the spotlight. The SCDA is a powder which has expansive strength when it is mixed with water. In these Characteristics, SCDA can destroy the concrete or rock as it is poured into boreholes of the concrete or rock structures. However, there is no industrial standard for the use of SCDA effectively yet. In this study, experimental study to measure the expansive pressure was conducted depending on various boundary conditions such as waterproof, length of the steel pipe, submerged of steel pipe. Furthermore, computational analysis using damage plasticity model to predict the minimum required pressure of the SCDA for the concrete demolition depending on spacing between holes(k-factor) and compressive strength of the concrete was conducted. Obtained results indicates that water heat dissipation with submerged steel pipe shows the stable pressure for measuring the SCDA and hole distance(k-factor) is the most important factor for crack initiation of concrete.
비폭성 파쇄제를 이용한 구조물 파괴에서 재료강도에 따른 균열 진전 해석
남윤민(Yunmin Nam),조황기(Hwangki Cho),손동우(Dongwoo Sohn) 대한기계학회 2016 대한기계학회 춘추학술대회 Vol.2016 No.12
One of traditional method for breaking large structures is the use of dynamite. However, such a blasting method has limitations due to noise and vibration problems. Recently, as an alternative to the blasting method, non-explosive demolition agents are considered to resolve the environment problems, In this study, we conduct a series of numerical simulations of breaking brittle structures that result from thermal expansion of the soundless chemical demolition agent (SCDA), one of non-explosive demolition agents. For two-dimensional semi-infinite structures, we observe the crack paths depending on the SCDA arrangement. Furthermore, we discuss the effect of material strength on breaking the structures.